Isolation and characterization of dracotoxin from the venom of the greater weever fish Trachinus draco.

Dracotoxin, a protein possessing toxic, membrane depolarizing and hemolytic activities, was isolated from the crude venom of the greater weever fish Trachinus draco. The purification involved ammonium sulfate precipitation of crude venom followed by gel filtration on a high performance liquid chromatograph column. About 300 micrograms of dracotoxin was obtained from 18 mg of crude venom proteins extracted from one average size fish. Dracotoxin consists of a single polypeptide of about 105,000 mol. wt. It hemolyzed rabbit erythrocytes with an EC50 of 3 ng/ml. Rabbit erythrocytes possessed binding sites for dracotoxin on their surface. Preincubation of dracotoxin with rabbit ghosts increased its EC50 value for rabbit erthrocytes from 3 to 25 ng/ml. Incubation of dracotoxin with enriched glycophorin fraction from rabbit erythrocytes also led to an increase in the EC50 to 70 ng/ml. The high specificity of dracotoxin for rabbit erythrocytes resembles that of staphylococcal alpha-toxin. Dracotoxin, however, caused hemolysis even at 4 degrees C and did not interact with cholesterol indicating substantial differences between the two hemolysins. Dracotoxin represents a major toxic component of T. draco venom.